Many industrial applications require the use of a material that is capable of generating a pulse of energy in a short amount of time. Such applications include but are not limited to fuses or igniters for pulse producing, gas producing, light producing, flame producing, and shock wave producing media. These fuses or igniters are particularly useful for projectiles, flying objects, and missiles as well as for firing explosives and igniting propellant charges and pyrotechnic charges. Alternative applications include chip-integrated ultra-fast heating elements for mass spectrometry or for the destruction of EPROMs. These substances require high energy densities and high energy liberation rates in comparison with conventional reactive materials.
Various parameters have been used to characterize explosive materials. For example, high temperature (12,000 K); fast reaction progress (greater than 104 m/s); and high energy density (28 kJ/g) are a few known parameters.
Diener et al. (U.S. Pat. No. 6,803,244) describe a nanostructured reactive substance and process for producing same by intermixing silicon and an oxidizing agent on a nanometer size scale. The fuel and the oxidizing agent are separated by a barrier layer. When the barrier layer is broken open, the fuel and oxidizing agent make contact and react, liberating energy. The source of silicon for the application is porous silicon produced by electrochemical etching of crystalline silicon (silicon discs, wafers). A spongy structure including a silicon lattice and pores or cavities (holes) results. Oxidizing agents are introduced into the pores. The surface of the remaining silicon structures is covered with a monolayer of atomic hydrogen. The silicon-hydrogen bond at the surface of the nanostructured lattice is relatively weak and thus the mixture of the fuel (silicon) and oxidizing agent which is present on the nanometer size scale in the pores is relatively unstable. It is necessary to effect additional passivation of the surface of the silicon lattice in order to increase stability. This is accomplished by heat treatment of the samples in an oxygen atmosphere, thus forming a barrier or protective layer and increasing stability of the samples when the pores are filled with an oxidizing agent. Powders have been formed from small, nanometer-size silicon particles (colloids) in addition to etching pores into a solid piece of silicon. Solid bodies have been formed by enclosing the silicon particles with a layer of oxidizing agent and then compacting them. The thickness of the barrier or protective layer applied to or encasing the silicon particles determines the spacing of the particles. Alternatively, individual silicon nanocrystals are interconnected by surface atoms on the silicon particles. In this instance, the functional groups function as spacers and also as a provider for an oxidant. The advantage is that there are no connecting arms between the nanometer-size silicon structure which can easily break under the effect of an impact, causing an unintended reaction. Although the compactable body can be geometrically freely shaped, the resulting shape is rigid and not flexible. Hence, flexible materials such as tapes, films, and wires cannot be produced.
Hoffman et al. (U.S. Pat. No. 6,984,274) describe an explosive composition comprising a porous fuel and an oxidizer. The porous fuel is a solid, preferably in the form of a structurally stable shaped body in which the fuel is present as a rigid structural matrix, such as porous silicon. The inner surface of the fuel is at least partially saturated with oxygen or modified in another way so as to increase the activation energy that has to be overcome so that there can be a reaction with the oxidizer. Typically, passivation takes place by heating the fuel in an atmosphere containing oxygen or in air. A less reactive protective layer is found on the surface of the nanocrystals. This passivation layer can be applied subsequently onto the porous fuel and can consist of an inert material (Teflon). Since the fuel is present in the form of a solid, shape imparting matrix, the composition is typically used as a load-bearing component in pyrotechnical devices or as a detonating agent or a component of an igniter. However, this material is not suitable for making flexible articles, films, wires or tapes.
An object of the present invention is to provide a shaped, flexible fuel.
Another object of the present invention is provide an energetic system which employs the shaped, flexible fuel.